What does horizontal gaze nystagmus refer to?

Horizontal gaze nystagmus refers to an involuntary jerking of the eyes that occurs when they are moved to the side. This phenomenon is often observed in individuals under the influence of certain substances, including alcohol. During a horizontal gaze nystagmus test, a law enforcement officer will track the movement of the eyes as they follow an object moving horizontally. The presence of nystagmus can indicate impairment or intoxication because it typically reflects a disruption in the vestibular and neurological functions that maintain eye stability.

The reason this answer is the most accurate is that it specifically describes the eye movement characteristic of horizontal gaze nystagmus, which is a key tool used in field sobriety tests to assess a driver's level of impairment. Other choices do not accurately describe this physiological response or provide relevant information about horizontal gaze nystagmus. For instance, involuntary limb movement, difficulty walking, or indications of low blood sugar do not pertain to the specific eye movements associated with this condition.